Based upon the fact that the temperature of mother's milk is approximately 37° C., it has been recognized that milk/formula given to an infant or baby should be at approximately this temperature. Liquid above or below this temperature may be rejected by the baby. If the liquid is accepted and is too hot, the baby's lips and mouth may be burned. If the liquid is too cold, it may bring a case of indigestion.
In the past, the most common method for determining the temperature of the fed to a baby was simply the tactile feeling of the fingertip, the hand palm or inner side of the wrist of a person having access to the baby feeding bottle. The determination was therefore often unreliable as it simply depended upon the thermal feeling of a particular person and furthermore was not free from the influences of atmospheric or room temperature.
It is known to use temperature indicators that can display the temperature of the bottle contents. These may have the form of digital devices which are not integrated with the bottle, because they cannot withstand common bottle use like heating, cleaning and sterilizing. Quantitative temperature indicators that are not digital are for example glass bulb thermometers or thermochromatic strips with a temperature range.
Other feeding bottles are provided with qualitative temperature indicators that indicate when the contents of the bottle are too hot, too cold or when the contents are ‘OK’. These baby feeding bottles are unsatisfactory, as the caregiver wants to know the temperature of the contents. Caregivers want to know the temperature of the feed, so that they can decide if it is safe to feed their babies. Caregivers may define their own personal temperature range for feeding the baby. Some caregivers will find that the feed should be between 30 and 37° C., while others prefer a range of 35 to 37° C. These values may vary depending on the age of the baby. Newborns tend to be more sensitive to the temperature of their feed than older babies.
A problem with the generally known feeding bottles that are provided with temperature indicators is that, either they provide the user with wrong information concerning the actual temperature of the contents of the bottle, i.e. a too low temperature indication, or that it takes a long time for the temperature indicator to give the correct temperature. Both problems are associated with the thermal properties of the material of the wall of the feeding bottle. On the one hand there exists a temperature difference across the wall. On the other hand it takes an unacceptable long time for the wall to reach the same temperature as the contents of the bottle, or at least a temperature that is close to that temperature.
In United States patent document US 2007/0121702 a solution for the above general problem is proposed. US 2007/0121702 discloses a drinking cup for holding hot liquids. The cup has a wall member and a bottom member that together form an internal space in which the hot liquid can be held. The wall member is made from an insulating material and embedded in said wall member a thermometer is provided. The thermometer is visible from outside the cup. US 2007/0121702 further discloses in a first embodiment that the complete inner surface of the internal space is provided with a thermally conducting part that conducts heat better than the wall member material. The thermometer is in direct contact with the thermally conducting layer, which in turn is in direct contact with the liquid in the internal space.
In a second embodiment only a backside of the thermometer that is directed towards the internal space is covered with said thermally conductive material, whereby the thermometer is located in the lower part of the drinking cup.
By providing a thermally conductive material that is in direct contact with on the one hand the hot liquid and on the other hand with the thermometer, an improved heat transfer to the thermometer is achieved resulting in an improved and faster temperature reading.
It is a concern of the solutions proposed in US 2007/0121702 that these solutions are not suitable for a baby feeding bottle. A baby feeding bottle is used in mainly two positions. A first position in which the baby feeding bottle is being filled with milk and a second position in which the milk is fed to the baby and in which the baby feeding bottle is substantially turned upside down with respect to the first position. In the first position the milk or liquid in the bottle is located in the lower part of the feeding bottle. In the second position the milk or liquid is located in the upper part of the feeding bottle.
The second embodiment of US 2007/0121702 cannot be used with a baby feeding bottle as the thermally conductive material is not in contact with the contents of the drinking cup in the second position. Hence, this solution cannot provide an improved temperature read-out in the second position of the feeding bottle.
The first embodiment of US 2007/0121702 would in principle be able to provide an improved temperature read-out in both positions of the feeding bottle, however according to US 2007/0121702 this requires the complete inner surface of the internal space to be covered with the thermally conductive material. This raises the concern that the feeding bottle cannot be used together with a microwave oven, which is commonly used to heat the contents of the feeding bottle, and thus compromises the usability of the feeding bottle.